Skip to main content

Slowly Changing Dimensions

What is a Slowly Changing Dimension?
A Slowly Changing Dimension (SCD) is a dimension that stores and manages both current and historical data over time in a data warehouse. It is considered and implemented as one of the most critical ETL tasks in tracking the history of dimension records.
There are three types of SCDs and you can use Warehouse Builder to define, deploy, and load all three types of SCDs.
What are the three types of SCDs?
The three types of SCDs are:
Type 1 SCDs - Overwriting
In a Type 1 SCD the new data overwrites the existing data. Thus the existing data is lost as it is not stored anywhere else. This is the default type of dimension you create. You do not need to specify any additional information to create a Type 1 SCD.
Type 2 SCDs - Creating another dimension record
A Type 2 SCD retains the full history of values. When the value of a chosen attribute changes, the current record is closed. A new record is created with the changed data values and this new record becomes the current record. Each record contains the effective time and expiration time to identify the time period between which the record was active.
Type 3 SCDs - Creating a current value field
A Type 3 SCD stores two versions of values for certain selected level attributes. Each record stores the previous value and the current value of the selected attribute. When the value of any of the selected attributes changes, the current value is stored as the old value and the new value becomes the current value.



Comments

Post a Comment

Popular posts from this blog

DataZen Syllabus

INTRODUCTION TO DATAZEN PRODUCT ELEMENTS ARCHITECTURE DATAZEN ENTERPRISE SERVER INTRODUCTION SERVER ARCHITECTURE INSTALLATION SECURITY CONTROL PANEL WEB VIEWER SERVER ADMINISTRATION CREATING AND PUBLISHING DASHBOARDS CONNECTING TO DATASOURCES DESIGNER CONFIGURING NAVIGATOR CONFIGURING VISUALIZATION  PUBLISHING DASHBOARD WORKING WITH MAP  WORKING WITH DRILL THROUGH DASHBOARDS
67 comments
Read more

MS BI Syllabus

Microsoft Business Intelligence Course Syllabus SSRS – SQL Server Reporting Services  Getting Started 1. Understanding Reporting (Authoring,Management,Delivery) 2. Installing Reporting (Native Mode, SharePoint Integration mode) 3. Building your first report  Authoring Reports 1. Developing Basic Reports (RDL,wizard,designer,datasource,dataset,formatting) 2. Working with expressions (expression to calculate value, Agg functions, exp for objects) 3. Organizing Data (Data Regions, Table, Matrix, Chart, List) 4. Advance Report (Parameter, drill down, drill through, links, 5. Report Model (Data Source, Data Source View, Model , Report Builder 3.0)  Managing Report ( Report Manager) 1. Managing Content (deploying report, folders, linked reports, datasources, value etc) 2. Managing Security (Item Level , Site navigation, localhost – sql) 3. Managing Server Config (Config Manager, Report Manager, Report Server DB)  Delivering Report 1. Accessing Report (Viewing...
31 comments
Read more

PowerBI Interview Questions and Answers

Power BI Interview Questions – General Questions 1). What is self-service business intelligence? Ans: Self-Service Business Intelligence (SSBI) is an approach to data analytics that enables business users to filter, segment, and, analyse their data, without the in-depth technical knowledge in statistical analysis, business intelligence (BI). SSBI has made it easier for end users to access their data and create various visuals to get better business insights. Anybody who has basic understanding of the data can create reports to build intuitive and shareable dashboards. 2). What are the parts of Microsoft self-service business intelligence solution? Ans: Microsoft has two parts for Self-Service BI  Excel BI Toolkit – It allows users to create interactive report by importing data from different sources and model data according to report requirement.  Power BI – It is the online solution that enables you to share the interactive reports and queries that you have created using ...
7 comments
Read more